This invention relates to a gas burning direct vent fireplace having a glass access door fitted at the room facing front of the firebox, and more particularly to an extended life sealing system for sealing the access door against leakage of flue gases into the room.
In direct vent fireplaces of the type illustrated in Shinek et al U.S. Pat. No. 4,793,322, the firebox, i.e., the combustion chamber or housing within which the hot flue gases are generated, vents directly through an outside wall to the exterior of the building in which the room is located and receives the fresh air which supports combustion from substantially that same exterior location. Room air is drawn through the front of the fireplace below the firebox, rises above the firebox over the top and exhausts at the front. As the room air flows about and over the firebox, it is heated so that it enters the room as heated air. An array of artificial logs or the like may be disposed within the firebox and gas, such as natural gas or propane, may be ignited to create a flame which in conjunction with the logs simulates the aesthetics of actual burning logs. The front of the fireplace, between the locations where the air enters from the room and where the heated air returns to the room, general includes an access door which includes a tempered or ceramic glass in the central area for viewing the flames.
In the prior art an elastomeric silicone polymer gasket has been glued about the glass front to seal the room from the flue gases within the firebox. The silicone gasket provides a good seal. However, it does not have very high temperature characteristics. Additionally, the glue must also withstand the high temperatures of the flue gases so that expensive high temperature glues are required for securing the gasket to the glass. For example, at temperatures in the range of 575.degree. F. to 600.degree. F., a temperature to which the seal is exposed in this environment, silicone gaskets become hard and brittle, and thereby age or deteriorate rapidly. For example, failure of the gasket may occur over a two year period of time. For this reason the American Gas Association (A.G.A.) and the Canadian Gas Association (C.G.A.) have modified their standards by permitting additional leakage past the glass into the room so as to permit the use of fiberglass seals instead of the silicone. Fiberglass has substantially greater high temperature characteristics relative to silicone, but it is porous and does not provide a very effective seal. In fact, the A.G.A. and C.G.A. standards recognize this fact since the leakage now permitted by these standards is about twice as much as heretofore permitted visa vis silicone. In a well sealed room, the content of the air in the room may receive carbon monoxide by this additional leakage of flue gases. This may, over an extended period of time, result in deleterious effects on persons or articles within the room.